SYMPOSIA PAPER Published: 01 January 2009
STP48156S

Irradiation-Induced Growth and Microstructure of Recrystallized, Cold Worked and Quenched Zircaloy-2, NSF, and E635 Alloys

Source

This paper is devoted to the study of the effect of the texture, phase composition, and microstructure on the irradiation-induced growth strain (GS) of zirconium-based alloys. GS measurements and TEM microstructural examinations were performed on Zry-2, NSF, and E635 samples in the recrystallized, beta quenched and cold-worked (CW) conditions. The samples were irradiated in the BOR-60 reactor in the temperature range of 315–325°C up to a neutron fluence level of 1.1 × 1026 n/m2 ( E>1 MeV ), i.e., up to a damage dose of 23 dpa. Growth strains of NSF and E635 alloys in all states and in the longitudinal and transverse directions are lower as compared to those of Zry-2, and do not exceed 0.2 % even at the maximum fluence level. As for recrystallized Zry-2, the GS kinetics are characterized by the appearance of the accelerated growth stage. A combination of a certain amount of Nb, Fe, and Sn in the matrix content plays a key role in GS kinetics. The higher the degree of CW, the higher the irradiation growth but its rate of increase with increasing fluence is different for alloys of different compositions. The maximum GS, reaching 0.72 %, is observed in the 20 % CW Zry-2 samples. Texture, along with the alloy composition, is one of the main GS-determining factors. Irradiation growth of the transversal samples is lower as compared to the longitudinal ones because of texture. As for quenched alloys, the texture is practically isotropic and GS values are low, independent of the alloy composition. In CW materials, the density of ‹c›- dislocations greatly affects the irradiation growth strain. Particles of Zr(Fe,Cr)2 and Zr2(Fe,Ni) phases in Zry-2 as well as Zr(Nb,Fe)2 in NSF and E635 are depleted in iron under irradiation. The Fe goes into the matrix and modifies its properties. The HCP lattice structure in the Laves phases in NSF and E635 changes into BCC (β-Nb-type). FCC (Zr,Nb)2Fe precipitates preserve on the whole their composition and structure; no amorphization of the Nb-containing precipitates is observed. The Zr2(Fe,Ni) precipitates with a BCT lattice remain crystalline, and HCP Zr(Cr,Fe)2 precipitates undergo amorphization. The average particle size in the irradiated alloys is larger and the concentration is a little lower as compared to the unirradiated ones. Irradiation-induced fine dispersed precipitates about 3 nm in size, probably enriched in niobium, appear in NSF and E635. The observed changes of microhardness are discussed from the viewpoint of generation of radiation defects (clusters, dislocation loops), evolution of the initial dislocation structure, and matrix composition (enrichment in Fe, Cr, and, probably, Nb).

Author Information

Kobylyansky, G., P.
FSUE SSC RIAR, Russia, Ulyanovsk region, Dimitrovgrad
Novoselov, A., E.
FSUE SSC RIAR, Russia, Ulyanovsk region, Dimitrovgrad
Ostrovsky, Z., E.
FSUE SSC RIAR, Russia, Ulyanovsk region, Dimitrovgrad
Obukhov, A., V.
FSUE SSC RIAR, Russia, Ulyanovsk region, Dimitrovgrad
Shishin, V., Yu.
FSUE SSC RIAR, Russia, Ulyanovsk region, Dimitrovgrad
Shishov, V., N.
FSUE VNIINM, Russia, Moscow
Nikulina, A., V.
FSUE VNIINM, Russia, Moscow
Peregud, M., M.
FSUE VNIINM, Russia, Moscow
Mahmood, S., T.
Global Nuclear Fuel, USA
White, D., W.
Global Nuclear Fuel, USA
Lin, Y, -P.
Global Nuclear Fuel, USA
Dubecky, M., A.
Global Nuclear Fuel, USA
Price: $25.00
Contact Sales
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Developed by Committee: B10
Pages: 564–582
DOI: 10.1520/STP48156S
ISBN-EB: 978-0-8031-8007-9
ISBN-13: 978-0-8031-4514-6